O2 Oxygen Sensor Upstream Downstream for Subaru Forester (2011-2013) 2.5L Non-Turbo

Direct-Fit Upstream & Downstream O2 Sensor Kit for 2011-2013 Subaru Forester (SH)

What it Does: This matched upstream and downstream oxygen sensor kit monitors exhaust air-fuel ratio and catalyst efficiency on 2011-2013 SH Forester FB25 2.5L DOHC engines.

The Stock Subaru Forester Sensor Failure

On the SH Forester equipped with the FB25 2.5L DOHC engine, factory upstream air-fuel and downstream oxygen sensors endure severe thermal cycling inside the exhaust stream. Over time, carbon buildup, flat-four oil ash, and internal heater element wear cause sluggish voltage switching or open circuits. When sensor output drifts, the ECM loses accurate closed-loop lambda feedback and logs fault codes such as P0133, P0031, or P0420.

Common Symptoms of a Failing OEM Oxygen Sensor

• Check Engine Light / DTCs: Slow response or heater faults trigger P0133, P0171, P0031, or P0420.
• Rich Fuel Trims: Skewed lambda feedback forces open-loop fueling, fouling plugs and hurting economy.
• Emissions Failure: Sluggish sensor switching causes rough idle and failed OBD-II readiness monitors.

The Direct-Fit Heated Zirconia Sensor Solution

Replacing both sensors together restores factory closed-loop fuel control across the FB25 2.5L DOHC exhaust system. Each unit uses a corrosion-resistant stainless housing, high-temp ceramic sensing element, and precision internal heater for fast cold-start light-off. Factory-length shielded leads and keyed OE connectors plug directly into the SH harness without splicing. Built to OE specs for 234-9109, 234-4513, and 22641-AA610, this matched kit restores accurate air-fuel stoichiometry.

What's Included

• 1 Upstream Oxygen Sensor
• 1 Downstream Oxygen Sensor

Technical Specifications

Compatibility

• 2011-2013 Subaru Forester 2.5L Naturally Aspirated (DOHC Non-Turbo) — Uses 2 sensors (1 upstream, 1 downstream)
• Exclusions: Does NOT fit 2.5L turbocharged Forester XT or Subaru XV Crosstrek

Frequently Asked Questions & Fitment Warnings

Does this fit the SH Forester?

Yes. Direct fit for the 2011-2013 Subaru Forester with the FB25 2.5L DOHC non-turbo engine. Excludes the 2.5L turbo Forester XT and XV Crosstrek; confirm engine before ordering.

Will this clear P0133 or P0420 codes?

It resolves sensor faults. New sensors clear response and heater codes like P0133 and P0031, though a returning P0420 indicates a worn catalytic converter.

Are OEM-style connectors pre-installed?

Yes. Both sensors come pre-terminated for plug-and-play installation; keep the sensing element clean during threading and torque to spec.

The Subaru Precision Standard

Engineered for flat-four ECM precision, this matched kit keeps your SH Forester in clean closed-loop stoichiometry with zero check engine lights. Reliable sensor feedback maintains emissions compliance and smooth throttle response.